A dry etching exhaust gas containing a present halogen series gas, a CVD chamber exhaust gas containing an SiH4 (silane) gas as the main component, and an implantation or doping exhaust gas containing AsH3 (arsine) or PH3 (phosphine) as the main component, contain the above-mentioned main component gases together with a carrier gas such as N2 (nitrogen) gas, and the present halogen series gas or particles formed by decomposition or reaction of these materials in a production apparatus.
Heretofore, as a method for treating a present halogen series gas, a method classified as a thermal decomposition method, an adsorption method or a wet type absorption method has been employed. The thermal decomposition method decomposes a gas to be treated by heating or combustion in a combustion type exhaust gas-treating apparatus, the adsorption method is a dry type treating method having an activated carbon or zeolite packed as an adsorbent, and the wet type absorption method is a wet type treating method absorbing the present halogen series gas with a water, an alkaline solution such as sodium hydroxide aqueous solution or an oxidation-reduction aqueous solution.
Among them, a dry type treating method using an activated carbon adsorbent as a packing material has been frequently used in order to make an apparatus smaller or to simplify operation and maintenance of the apparatus. However, there have been various problems such as a danger of fire by heat of adsorption of a gas to be treated, degradation of working environment at the time of exchanging a packing due to an odor of the present halogen series gas desorbed from an adsorbent used, and treatment of a solid waste. Also, it has been demanded to further increase an adsorption capacity of a packing in order to reduce times of exchanging operations of the packing. These problems were remarkable particularly at the time of removing a Cl2 gas or a mixture gas of Cl2 and BCl3 (boron trichloride), which has been frequently used.
In addition to the above methods for removing the present halogen series gas, there is a method of employing a chemical reaction, the treating capacity by which is expected to be improved. For example, there is disclosed a method of using a granule such as magnesium oxide (MgO) or sodium hydrogencarbonate (NaHCO3) (JP-A-61-61619, JP-A-62-42727 and JP-A-2002-143640). However, in order to practically work the above disclosed method, it is demanded to improve capacity at the time of treating the present halogen series gas which is rarefied and at a high linear velocity, and it is required to achieve improvement on a reaction rate for a long life by an inexpensive, safe and convenient method. Also, in a semiconductor equipment, several kinds of gases are used for one apparatus, and it is therefore demanded to remove various present halogen series gases by one removing agent. Further, according to a method including an adsorption method by an activated carbon, it was difficult to predict the end of reaction, and therefore it was usually confirmed by checking discoloration of an indicator reagent at the outlet of a packed bed after the fact. Further, its life was estimated by measuring a weight increase of a packed bed, but it was difficult to effect accurate estimation since the weight changes after the reaction depending on the composition of a gas to be treated.
In order to solve the above-mentioned problems, the present invention provides a method of removing a present halogen series gas, which enables to enhance a performance of treating the present halogen series gas, to prevent firing of the adsorbent, to reduce an odor of the adsorbent used and generation of a solid waste, and to make estimation of the life of a removing agent easy, thereby improving a semiconductor production process.